Currently this is the NSC level 5 thruster added to the vanilla thruster chain.

This thruster is part of the NSC Component Feature, and are accessible to all NSC Players who do not use another popular Stellaris component mod, such as NHunter’s Extra Ship Components, TFW’s Bunch of Ship Parts, or Guilliman’s Crystallis. If you have one of these mods active alongside NSC, NSC will not give you the NSC Components Feature, to allow you to use only utilize one component mod set to avoid clutter in your component lists. However, inside the NSC Features Menu will be a new option allowing you to gain access to the NSC Component Feature even if you have another component mod to give you the choice.

IMPORTANT: As of this writing, only the ESC mod is currently setup to support the NSC Component Feature. BOSP & Crystallis support is currently in development, and this line will be updated to inform you when support for the latter two mods becomes available.